This invention relates generally to programmable controllers, and more specifically to programmable controllers for controlling the operation of electro-mechanical devices.
Conventional programmable controllers generally employ a microprocessor which is programmed to cause selected electro-mechanical devices (motors, solenoids, etc.) to operate in a predetermined sequence. Generally, the system utilizing the controller also includes sensors which detect the movement or operation of the electro-mechanical devices. The microprocessor, in turn, may continuously strobe the sensor to determine when the electro-mechanical devices have completed their assigned functions.
Although controllers utilizing microprocessors generally operate well, they suffer from the fact that a fairly large memory is required to carry out the type of functions described above. Hence, microprocessor controllers have been too expensive for some applications. Even more significantly, there are circumstances in which it is highly desirable to be able to change the sequence of operations of the electro-mechanical devices without incurring the expense of reprogramming a microprocessor. For example, in the field of immunology where laboratory samples are processed, sampled, and the like according to a known procedure, that procedure is subject to frequent change as advances are made in the art. To reprogram, test and de-bug a microprocessor to keep abreast of changes in the immunology art would be undesirable from a time and complexity standpoint. Hence, microprocessor controllers are undesirable from a complexity and/or cost standpoint for a variety of applications.